The Evolution of Colchicaceae, with a Focus on Chromosome Numbers
The Evolution of Colchicaceae, with a Focus on Chromosome Numbers
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DOI：
10.1600/036364414x680852
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发表时间：
2014-04-01
影响因子：
1
通讯作者：
Renner, Susanne S.
中科院分区：
文献类型：
--
作者：
Chacon, Juliana;Cusimano, Natalie;Renner, Susanne S.
秋水仙科是一种地生草本植物，除新热带外，分布在各大洲。非洲南部尤其多样化，270种中有80种出现在那里。秋水仙科表现出广泛的倍性水平，从2n = 14到2n = 216。为了了解这种细胞遗传多样性是在哪里以及如何产生的，我们对秋水仙科和秋水仙枝进行了多位点系统发育，分别包括85种和137种以及相关的外群。为了推断可以解释现存物种中观察到的数量的事件类型（异倍体、多倍体或半重复，即不同倍体配子的融合），我们比较了一系列关于系统图的似然模型、惩罚似然超谱树和放松时钟计时图，其中包含58或112种已发表的染色体计数。虽然这些模型涉及简化，不能解决染色体重排背后的过程，但它们可以帮助构建关于染色体数量在充分抽样的群体中变化方向的问题。结果表明，在秋水仙科中，除我们推断频繁的半重复外，异倍体在秋水仙科中起着很大的作用。虽然已知三倍体促进四倍体的固定，并且植物物种通常包括奇数倍体水平的个体（三倍体，五倍体），但在没有分子细胞遗传学工作和实验杂交数据的情况下，我们不愿意接受系统发育推断的情景。
The lily family Colchicaceae consists of geophytic herbs distributed on all continents except the Neotropics. It is particularly diverse in southern Africa, where 80 of the 270 species occur. Colchicaceae exhibit a wide range of ploidy levels, from 2n = 14 to 2n = 216. To understand where and how this cytogenetic diversity arose, we generated multilocus phylogenies of the Colchicaceae and the Colchicum clade that respectively included 85 or 137 species plus relevant outgroups. To infer the kinds of events that could explain the observed numbers in the living species (dysploidy, polyploidization, or demi-duplication, i.e. fusion of gametes of different ploidy), we compared a series of likelihood models on phylograms, penalized likelihood ultrametric trees, and relaxed clock chronograms that contained the 58 or 112 species with published chromosome counts. While such models involve simplification and cannot address the processes behind chromosomal rearrangements, they can help frame questions about the direction of change in chromosome numbers in well-sampled groups. The results suggest that dysploidy played a large role in the Colchicaceae, with the exception of Colchicum itself for which we inferred frequent demi-duplication. While it is known that triploids facilitate the fixation of tetraploidy and that plant species often include individuals of odd ploidy level (triploids, pentaploids), we hesitate to accept the phylogenetically inferred scenario without molecular-cytogenetic work and data from experimental hybridizations.